76 OSTEOLOGY [Parr IT. 
occipital foramen; in the great pneumaticity of the cranium; in the ratio of the upper 
mandible to the cranium; in the retrogression of the ethmoidal fossz; in the absence 
of the frontal protuberance ; and of the lateral excavations of the upper mandible. Such, 
then, are some of the more important and characteristic distinctions ; without entering mto 
superfluous details, regarding the differences in the minute configuration of similar parts, as 
these may vary even in the same group. 
The Cathartes resembles the Dodo, in the absence of the ossified vomer; in the anchy- 
losis of the prefrontal ; in the retrogression of the ethmoidal fossee ; in the breadth of the 
interorbital region; and in the curvature of the lower jaw. It differs, however, in other 
more important characters, common to it with the typical Vultures, and is peculiar in 
possessing the nasal vestibule, characteristic of the Cathartine modification of the raptorial type. 
From the typical Rasores, the Dodo differs, in the elongation of the external nasal 
orifice ; in the greater development of the maxilla; in the obliquity of the zygoma; in the 
greater complexity of the palatine bone; im the double mastoid condyle of the tympanic ; 
in the absence of the posterior and internal angular processes of the basal facet of the lower 
jaw ; in the anchylosis of the prefrontal, and great development of its inferior process ; in the 
presence of the ale of the ethmoid ; in the retrogression of the ethmoidal fossz ; in the 
great pneumaticity of the prefrontal, and of the sphenoidal rostrum ; and in the absence of the 
mesial supra-occipital foramen. 
The skull of Pterocles resembles that of the Dodo in the same degree as it approaches 
the type of the Columbide. 
From the Insessores, the Dodo is at once distinguished by the form of the palatine 
bone; by the absence of the vomer; by the elongation of the external nasal fissure ; by the 
obliquity of the zygoma; and by the relation of the antorbital process to the prefrontal. 
It would be useless to state the essential differences between the skull of the Dodo, and 
that in the different families of the Grallatorial and Natatorial orders, as no one is likely to 
suppose that it has any affinity with either of these groups. 
I now proceed to describe the skull of the Dodo in greater detail. 
The posterior subelliptical facet of the cranium, is formed by the occipital bone ; its greater diameter 
is transverse, and measures two inches and eight lines and a half; and its lesser, one inch and seven lines 
and a half. It presents an upper crescentic segment, with a vertical plane, embracing in its concavity a 
lozenge-shaped surface, which inclines obliquely downwards and forwards at an angle of 125°. 
The upper convex margin corresponds to the supra-occipital mdge, contmued on each side into the 
convex incurving border of the paroccipital process, which projects outwards, forming the posterior wall of 
the tympanic cavity. The infra-occipital ridge, forming the central moiety of the concave edge, overhangs 
the recess perforated by the foramen magnum, like the dripstone of a Gothic arch; a lme drawn from its 
corbal-like origin outwards, on each side, to the inferior angle of the paroccipital process, indicates the 
remainder of this boundary ; along which the vertical supra-occipital surface is broadly rounded off into the 
thomboidal fossa, occupying the lateral angle of the lozenge. This depression is bounded externally by 
